Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, 10691 Stockholm, Sweden.
Chemistry. 2010 Feb 22;16(8):2537-46. doi: 10.1002/chem.200902278.
Azapropanedithiolate (adt)-bridged model complexes of [FeFe]-hydrogenase bearing a carboxylic acid functionality have been designed with the aim of decreasing the potential for reduction of protons to hydrogen. Protonation of the bisphosphine complexes 4-6 has been studied by in situ IR and NMR spectroscopy, which revealed that protonation with triflic acid most likely takes place first at the N-bridge for complex 4 but at the Fe-Fe bond for complexes 5 and 6. Using an excess of acid, the diprotonated species could also be observed, but none of the protonated species was sufficiently stable to be isolated in a pure state. Electrochemical studies have provided an insight into the catalytic mechanisms under strongly acidic conditions, and have also shown that complexes 3 and 6 are electro-active in aqueous solution even in the absence of acid, presumably due to hydrogen bonding. Hydrogen evolution, driven by visible light, has been observed for three-component systems consisting of Ru(bpy)(3), complex 1, 2, or 3, and ascorbic acid in CH(3)CN/D(2)O solution by on-line mass spectrometry.
设计了具有羧酸官能团的 [FeFe]-氢化酶的 azapropanedithiolate (adt)-桥接模型配合物，目的是降低质子还原为氢的潜力。通过原位 IR 和 NMR 光谱研究了双膦配合物 4-6 的质子化，结果表明，三氟磺酸的质子化最有可能首先发生在复合物 4 的 N-桥上，但在复合物 5 和 6 中则发生在 Fe-Fe 键上。使用过量的酸，也可以观察到二质子化物种，但没有一种质子化物种足够稳定，可以在纯态下分离出来。电化学研究深入了解了强酸性条件下的催化机制，还表明即使在没有酸的情况下，配合物 3 和 6 在水溶液中也是电活性的，这可能是由于氢键的作用。通过在线质谱法，在 CH(3)CN/D(2)O 溶液中，由 Ru(bpy)(3)、配合物 1、2 或 3 和抗坏血酸组成的三组分系统在可见光的驱动下观察到了氢的释放。
